This is company dependent rather than country. When I was early in my career as a software dev I felt like I could never say no. I would continue to take on additional work which translated to more hours.

Eventually my manager at the time did the best thing he could for me. He asked me into his office for a "talk". Then he told me that he didn't want to lose me because I burned out. He said, "Look, you have to learn to say no to people. If you aren't comfortable doing that then tell them to run it by me; and then I'll say no."